The activation of gonadotropin-releasing hormone (GnRH) neurons is key to the successful initiation of puberty. However, the mechanisms by which this occurs are not well understood. Strong evidence supports a role for the kisspeptin-GPR54 system as a central contributor to this process. Humans and mice with inactivating mutations of the G protein-coupled receptor GPR54 have low gonadotropin levels and fail to undergo normal puberty. Also, the central administration of kisspeptin, the ligand of GPR54, in mammals stimulates the release of GnRH and gonadotropins. These observations suggest a direct effect of kisspeptin on GnRH release. The long-term goal of this proposal is to gain a better understanding of the molecular mechanisms by which GPR54 and kisspeptin regulate the function of the GnRH neuron in the development and maintenance of reproductive capability. The central hypothesis for this research is that GPR54 contributes to GnRH neuronal development and serves to regulate hypothalamic GnRH release. To address this hypothesis, three specific aims are proposed: 1) Validation of specific gene targets of GPR54 activation identified by DNA microarray analysis; 2) Analyze intracellular signal transduction pathways activated by GPR54 in GnRH neuronal cell cultures as these pathways may be active in kisspeptin-stimulated GnRH release or in regulated genes; and 3) Characterize the physiologic significance of GPR54 in GnRH neurons in vivo using a tissue-specific knockout mouse model. A more detailed understanding of GPR54 regulation of GnRH neuronal function is essential to advance our knowledge of the role of this receptor and its cognate ligand, kisspeptin, in reproductive competency. Under this proposal, the candidate will receive intensive research training under the mentorship of Dr. Ursula Kaiser, allowing her to develop the expertise needed to become an independent investigator in the field of reproductive endocrinology at the molecular level. The public health relevance of this work is that its successful completion will guide the development of new and innovative approaches to diagnosis and treatment of human diseases that affect fertility, such as abnormal puberty, polycystic ovarian syndrome, endometriosis, and hormone-dependent cancers that collectively affect millions of Americans annually. [unreadable] [unreadable] [unreadable]